Functionalized green filtration media for passive underground drainfield for septic tank nutrient removal

ABSTRACT

Methods, systems and compositions for a green sorption media for bioretention soil amendments in drainfields for on-site waste water systems filled with the green sorption media to foster an anaerobic or anoxic environment saturated. The green sorption media includes one or more recycled materials, including tire crumb, sawdust, orange peel, coconut husks, leaf compost, oyster shell, soy bean hulls and one or more naturally occurring materials including peat, sands, zeolites, and clay. The wastewater filtration system for a passive drainfield includes the green sorption material mixture, a cell including baffled compartments and a riser, the cell filled with green sorption material mixture to provide an alternating cycle of aerobic and anoxic environments, an influent distribution system to distribute the influent over the cell, and a piping system arranged for dosing the cell to sustain the functionality of the green sorption material mixture to remove nutrient content in wastewater.

FIELD OF THE INVENTION

This invention relates to wastewater treatment and, in particular, tomethods and systems and compositions for on-site wastewater treatmentusing a combination of recycled materials and natural sorption andfilter media for the removal of nutrients from septic tank effluent,including phosphorus and nitrogen that are harmful to the environment.

BACKGROUND AND PRIOR ART

Nitrate in drinking water systems usually originates from fertilizers orfrom animal or human wastes. Nitrate concentrations in the natural watersystem tend to be highest in areas of intensive agriculture or wherethere are many septic systems. High nitrogen and phosphorus content inthe water body has impeded water reuse potential and impacted ecosystemintegrity and human health. Nitrate (NO₃ ⁻) can potentially be toxic andcan cause human health problem such as methemoglobinemia, liver damageand possible cancers according to a World Health Organization, 2006report. Phosphorus can potentially trigger the eutrophication issues infresh water bodies, which could result in toxic algae and endanger thesource of drinking waters eventually (ESA, 2000).

When urban regions gradually expand due to regional development,centralized sewage collection, treatment, and disposal is oftenunavailable for both geographic and economic reasons. Thus,decentralized or on-site wastewater treatment systems (OWTS) may benecessary to protect public health. Nationwide, wastewater effluent fromon-site wastewater treatment systems can represent a large fraction ofnutrient loads to groundwater aquifers.

In the modern era, on-site wastewater treatment systems also referred asseptic system primarily includes a septic tank and soil adsorption fieldor drainfield also known as subsurface wastewater infiltration systems.Drainfields are located in permeable, unsaturated natural soil orimported fill material so wastewater can infiltrate and percolatethrough the underlying soil to the ground water thereby treating itselfthrough a variety of physical, chemical, and microbiological processes.However, the nitrate ion (NO₃ ⁻) and soil are negatively charged, and sothe NO₃ ⁻ ion is not bound to the soil. Therefore, nitrate ions movefreely with the soil solution and are readily leachable. Nitrogen,particularly nitrates, easily moves from terrestrial ecosystems intosurface and groundwater, including lakes, streams, rivers, and estuariesas described in Peterjohn et al., Symptoms of nitrogen saturation in twocentral Appalachian hardwood forest ecosystems. Biogeochemistry 35, pp.507-522 (1996).

Two important processes that result in the transformation of nitrate arenitrification and denitrification. Nitrification is a process in whichammonium is oxidized and denitrification is a process in which nitrateis reduced back to nitrogen gas before escaping into the air. However,only denitrification that is a microbiologically mediated processoccurring under anaerobic (oxygen depleted) conditions can result in thepermanent removal of nitrate. Approximately, 55-85% of the nitrogen thatenters the septic tank is available to ground water mainly in the formof nitrates as described in Stoltz and Reneau, Potential forContamination of Ground and Surface Waters from On-site WastewaterDisposal Systems (1998). Based on recent Florida research data, a familyof four discharges approximately 11.36 Kg (25 pounds) of nitrogen(measured in the form of nitrates) per year into the drainfield of aconventional onsite sewage treatment and disposal system according to aFlorida Department of Health report dated 2004.

The main risks of nitrates pollutants are in “Blue baby” syndrome andsuspected carcinogenic effect of nitrates on humans, and the nutrientenrichment of receiving waters. It has regulatory health limits in theUnited States of maximum contamination level (MCL) of 10 mg-N L⁻¹. Aseptic tank with a conventional drainfield does not typically removenitrogen in the form of nitrates since it is very soluble and does notsorb well to soil components during infiltration.

The use of different sorption media in septic tank drainfields turns outto be an appealing engineering approach in dealing with the increasingtrend of higher nitrate concentrations that is expected to continue inthe surface and groundwater systems. Besides, the use of the sorptionmedia for denitrification rather than traditional gravel-filleddrainfield for handling the effluents from the septic tank system wouldbecome a new focus in rural communities. Large-scale implementation withdifferent sorption media to remove nutrients will be popular in thefuture. See Mothersill, C. L., Anderson, B. C., Watt, W. E., andMarsalek, J., Biological filtration of stormwater: field operations andmaintenance experiences and Birch, G. F., Fazeli, M. S., and Matthai,C., Efficiency of an infiltration basin in removing contaminants fromurban stormwater, Environmental Monitoring and Assessment, 101, pp.23-38, (2005).

It is believed that functionalized sorption media might have a betterion exchange capacity to support adsorption/desorption capacity.Research that lead to the subject matter of the present inventionincluded screening sorption media via a thorough literature review,characterization of the selected sorption media, and examination oftheir sorption capacity for nutrient removal using column study,isotherm tests and microcosm assessment in support of the newunderground drainfield design as an integral part of modern septic tanksystem.

Many researchers had tried to remove nitrogen species by using sorptionmedia. Kim, H., Seagren, E. A., and Davis A. P., EngineeringBioretention for Removal of Nitrate from Storm water Runoff, in WEFTEC2000 Conference Proceedings on CDROM Research Symposium, NitrogenRemoval, Session 19, Anaheim Calif., October (2000) used different kindsof sorption media, such as alfalfa, mulch compost, newspaper, sawdust,wheat straw, wood chips for nitrate removal from storm water runoff.They found that alfalfa and newspaper had 100% nitrate removalefficiency but mulch compost had 60% nitrate removal efficiency. Theyalso found that sawdust, wheat straw and wood chips had good removalefficiency greater than 95%, but wood chips showed consistently betterperformance in nitrate removal over sawdust. From their experiment, itcould be concluded that all of these were electron donors and goodcarbon sources for promoting denitrification. They suggested thatincreasing the retention time may gain better removal efficiency. Kim etal. also found that soil could only remove 7% to 10% of nitrate due toits anionic form.

Güngör, K. and Ünlü K., 2005. Nitrite and nitrate removal efficienciesof soil aquifer treatment columns, Turkish J. Eng. Env. Sci., 29, pp.159-170, (2005) conducted nitrate and nitrite removal experiment byusing only three types of soils, including sandy clay loam, loamy sandand sandy loam. They found significant nitrate and nitrite removal(i.e., over 90%). Hsieh, C. H. and Davis, A. P., Multiple-event study ofbioretention for treatment of urban storm water runoff, DiffusePollution Conference Dublin, Ireland (2005) found that mulch was veryeffective in removing nitrate, unlike sand. But they had not gained goodammonia removal efficiency by using mulch. They concluded that soil withhigher silt/clay and cation (Mg/Ca/K) contents might be very effectivein nutrient removal. They also concluded that course media might not beable to retain the nutrient in repetitive loading due to small surfacearea so that sand should not be used.

Darbi, A., Viraraghavan, T., Butler, R., and Corkal, D., Batch studieson nitrate removal from potable water, Water South Africa, 28(3), pp.319-322, (2002) used sulfur and limestone for nitrate removal frompotable water. In their experiment, sulfur was used as an electron donorand limestone was used to maintain the pH. They found that the optimummixing ratio of sulfur and limestone is 1:1 for nitrate removal (i.e.,about 98% nitrate removal was observed). They also suggested thatincreasing the retention time may obtain higher nitrate removalefficiency. Lisi, R. D., Park, J. K., and Stier, J. C., MitigatingNutrient Leaching with a Sub-Surface Drainage Layer of Granulated Tires.Waste Management, 24(8), pp. 831-839, (2004) tried to use granulatedtire for the removal of nitrate. They found 48.000 g of tire crumb canremove 16.2 g of NO₃ ⁻—N. Sengupta, S. and Ergas, S. J., Autotrophicbiological denitrification with elemental sulfur or hydrogen forcomplete removal of nitrate-nitrogen from a septic system wastewater, areport submitted to

The NOAA/UNH cooperative institute for costal and estuarineenvironmental technology (2006) did an experiment to remove nitrate fromwastewater by using marble chips, limestone and oyster shell. Theirexperiment gave some significant outcomes about using those solids assorption media. They found that oyster shell containing almost 98% CaCO₃and limestone could remove 80% and 56% of nitrate, respectively. The pHand alkalinity were higher in testing using oyster shell rather thanlimestone and marble chips. Oyster shell was efficient to reduce nitriteaccumulation and dissolved oxygen did not work as a denitrificationinhibitor when oyster shell was used as a sorption media. From thesefindings, it can be concluded that oyster shell is much more effectivethan limestone or marble chips for removing nitrate. Oyster shell canalso be a good candidate for controlling the pH that is sensitive fordenitrification.

Savage A. J. and Tyrrel, S. F., 2005. Compost liquor bioremediationusing waste materials as biofiltration media, Bioresource Technology,96, pp. 557-564 (2005) used wood mulch, compost, soil, broken brick andpolystyrene packaging for removal of NH₃—N from compost leachate. Theyreached a conclusion that wood mulch (75%) and compost (55%) had betterremoval efficiency for NH₃—N than other media and polystyrene was theleast capable one to remove NH₃—N. Soil and broken brick could remove38% and 35% of NG₃—N, respectively. All these media had the samecapability to remove BOD₅ by microbial oxidation process. The researchgroup found that compost and wood mulch had a tendency to increase thepH. They concluded that specific surface area, void space, permeability,and adsorption capacity might influence the removal efficiency.

Phosphorus removal from storm water is both precipitation and adsorptionprocesses due to chemical reaction. As phosphorus has enormous effect onaquatic ecosystem, researchers have been trying to discover aneconomically feasible removal procedure. Some functionalized sorptionmedia that can be used for phosphorus removal are sand rich with Fe, Caor Mg, gravel, limestone, shale, light weight aggregates (LWA), zeolite(natural mineral or artificially produced alumino silicates), pelletedclay (along or in combination with soils), opaka (a siliceoussedimentary rock), pumice (natural porous mineral), wollastonite (acalcium metasilicate), fly ash, blast furnace slag (BFGS—a porousnon-metallic co-product in iron industry), alum, goethite (a hydrousferric oxide), hematite (a mineral form of iron(III) oxide), dolomiteand calcite as described in Korkusuz, E. A., Beklioglu, M., and Demirer,G. N., Use of blast furnace granulated slag as a substrate in verticalflow reed beds: field application, Bioresourse Technology, 98, pp.2089-2101, (2007).

DeBusk, T. A., Langston, M. A., Schwegler, B. R., and Davidson, S., 1997describes an evaluation of filter media for treating storm water runoff,Proceedings of the fifth Biennial Storm water Research Conference, pp.82-89 (1997) used sand with quartz, fresh organic peat soil, crushedlime rock (2.5 cm nominal size) and wollastonite (a mine containingcalcium metasilicate plus ferrous metasilicate) to remove phosphorus,nickel and cadmium from storm water. They found that wallastonite hadvery good removal efficiency for their targeted contaminants.Wallastonite could remove about 87.8% P, 97.7% Cd and 80.3% Ni. On theother hand, limerock, peat and sand could remove 41.4%, 44%, and 41.4% Prespectively. It was concluded that wallastonite is very effective inphosphorus removal because it contains calcium and ferrous ions. Calciumand ferrous ions can remove phosphorus by precipitation reaction oradsorption.

Hsieh and Davis (2003) found good total phosphorus (TP) removal (about41% to 48%) by sand and concluded that it might happen due to simpleadsorption or complex sorption/precipitation processes. They found thatmulch was not a good candidate for TP removal. This research groupconcluded that TP removal was highly variable and it might be related toproperties of sorption media used and flow pattern of nutrient ladenwater through the sorption media. Again, organic matter could alsoaccelerate TP removal up to 93%.

Clark, S., Pitt, R., and Brown, D., Effect of anaerobiosis on filtermedia pollutant retention, Presented at the Engineering Foundation andthe American Society of Civil Engineers Conference on Information &monitoring needs for evaluating the mitigation effects of BMPs,Snowmass, Colo. (2001) tried to remove contaminants in aerobic andanaerobic conditions from storm water runoff by using activated carbon,peat moss, compost and sand. They found good phosphorus removalefficiency by all four media in both conditions. They also found nodesorption condition in their system for phosphorus. But they observedthat sorption was better and leaching was lesser in aerobic conditionfor compost.

Forbes, M. G., Dickson, K. L., Saleh, F., Doyle, R. D., Hudak, P., andWaller, W. T., Recovery and fractionation of phosphate retained bylightweight expanded shale and masonry sand used as media in subsurfaceflow treatment wetlands, Environmental Science & Technology, 39(12), pp.4621-4627 (2005) used lightweight expanded shale and masonry sand forthe removal of phosphorus. They summarized that sand is a poor candidatefor retaining phosphorus and expanded shale has greater removalefficiency due to its larger surface area.

Researchers have used a variety of sorption media to remove nutrient,both nitrogen and phosphorus species, from storm water and wastewater.For removing nitrogen and phosphorus from storm water or wastewater,these filtration media can be further classified based on the derivationfrom: 1) plants or processed from components of plants; 2) sand andclay; 3) minerals; and 4) waste materials that may be recycled from thesociety.

Known prior art patents include U.S. Pat. No. 6,458,179 issued Oct. 1,2002 for the use of shredded rubber as one material in a fertilizer;U.S. Pat. No. 5,823,711 issued Oct. 20, 1998 discloses use of scrap andshredded tires for improved drainage; U.S. Pat. No. 5,509,230 issuedApr. 23, 1996 discloses a lawn protecting method and elastic body forlawn protection used to minimize compaction under turf grasses; U.S.Pat. No. 5,014,462 issued May 14, 1991 discloses use of a soil amendmentwith rubber particles for increased porosity and reduced compaction;U.S. Pat. No. 6,969,469 issued Nov. 29, 2005 is directed toward a methodof using waste tires as a filter media in a water treatment filteringdevice; and U.S. Pat. No. 6,214,229 issued on Apr. 10, 2001 discloses atreatment system for removing phosphorus from electric parts.

SUMMARY OF THE INVENTION

A primary objective of the present invention is to provide methods,systems and compositions for removing nitrogen and phosphorus found inseptic tank effluent that are harmful to the environment usingmaterials, compositions, and substances with different adequate recipesof green sorption media.

A secondary objective of the present invention is to provide methods,systems and compositions for an innovative passive undergrounddrainfield that is highly sustainable to fit in any landscape and builtenvironment on one hand, and highly applicable in dealing with any typeof septic tank systems on the other hand.

A third objective of the present invention is to provide methods,systems and compositions for on-site wastewater treatment using acombination of recycled materials and natural sorption and filter mediafor the removal of nutrients from septic tank effluent, includingphosphorus and nitrogen that are harmful to the environment.

A fourth objective of the present invention is to provide methods,systems and compositions for on-site wastewater treatment removingnutrients using mixtures of materials that provide for sorption, ionexchange, chemical precipitation, biological removal and filtrationalong with other processes in a well configured anoxic environment.

A fifth objective of the present invention is to provide methods,systems and compositions for on-site wastewater treatment using flexibleapparatus, devices, and utility with a lower maintenance burden and costimpact.

A sixth objective of the present invention is to provide methods,systems and compositions for wastewater treatment and management usingmicrobiological species to convert various species of nitrogen tonitrogen gases and custom mixes of materials based on the waste streamnutrient characteristics, residence time, and the projected life of theapplication.

A seventh objective of the present invention is to provide methods,systems and extended applications for wastewater treatment andmanagement for sources of nitrogen and phosphorus including industrialdomestic, agricultural overland flows, aquaculture operation, includingshrimp farm, fish farm, forest clearance, and geothermal inflows thatmight end up as enrichment of groundwater aquifers.

A first embodiment of the present invention provides a wastewaterfiltration system for a passive drainfield. The system includes a greensorption material mixture consisting of one or more recycled materialsmixed with one or more of a naturally occurring materials, a wetlandcell filled with the green sorption material mixture to provide ananoxic environment, the wetland cell including baffled compartments anda riser to host the anoxic environment, an influent distribution systemto distribute the influent over the wetland cell, and a piping systemarranged for dosing the wetland cell to sustain the functionality of thegreen sorption material mixture in the passive drainfield to remove anutrient content in wastewater. Proper design of hydraulic residence orretention time with appropriate baffled compartments and riser must bewell configured to host an anoxic environment.

The group of recycled materials includes tire crumb, sawdust, orangepeel, coconut husks, leaf compost, oyster shell, and soy bean hulls treebark, wood chips, paper, alfalfa, mulch, cotton and wheat straw and thegroup of naturally occurring materials includes peat, sands, zeolitesand clay. In an embodiment, the green sorption material mixture includesapproximately 68% fine sand, approximately 25% tire crumb, andapproximately 7% sawdust by volume. In another embodiment, the greensorption material mixture includes approximately 69% fine sand,approximately 25% tire crumb, and approximately 6% paper/newspaper byvolume. In an embodiment, one of the one or more recycled materials isselected from a subgroup including sawdust and paper as electron donorsin a drainfield and the recycled material is tire crumb for nutrientremoval based on an adsorption capacity of the tire crumb.

The filtration system can be an on-site wastewater treatment system, apassive underground drainfield to remove a nutrient content in septictank effluents and other waste streams in contaminatedwastewater/groundwater systems, a passive underground drainfield toremove a nutrient content in contaminated wastewater/groundwater system,a septic tank system, and/or an in-situ remediation of nitrate andortho-phosphate contaminated in groundwater.

A second embodiment provides a method for on-site wastewater treatmentincluding the steps of providing a wetland cell including baffledcompartments and a riser to host the anoxic environment, mixing one ormore recycled material selected from a group consisting essentially oftires, sawdust and food waste and one or more naturally occurringmaterials as a green sorption material mixture, filling the horizontalunderground cell with a green sorption material mixture to provide ananoxic environment, and providing a piping system for dosing the cellwith an influent to sustain the functionality of the green sorptionmaterial mixture in the passive drainfield to remove a nutrient contentin wastewater.

In an embodiment, the method is used in conjunction with undergroundseptic tank systems as an alternating cycle of aerobic and anoxicenvironments to remove nutrient content from the influent. Some verticalpipes for venting in the beginning close to the header pipe will inducesome amount of air into the initial cell so that the aerobic environmentcan be promoted periodically when needed. This will trigger thenitrification and denitrification processes as expected. Because of thisinvention, there is no need to separate the nitrification anddenitrification processes into two tanks and indirectly achieve the goalof cost effectiveness.

A third embodiment provides a passive underground drainfield includingan underground drainfield filled with a green sorption media andportioned by one or more baffles located on the sorption media to createone or more open channels, the baffles guiding a flow of influentfollowing the flow path shown through the open channel into the sorptionmedia. The system includes a distribution system for directing aninfluent into the underground drainfield, the distribution systemincluding perforated inlet pipes in each of the one or more openchannels to promote aeration to maintain an aerobic condition in eachchannel and an air inlet port 540 in each of the one or more channelsfor drawing air for nitrification for an anoxic and aerobic environmentwhere denitifcation occurs. A riser located at one end of theunderground drainfield in the sorption media and extending a distanceabove the sorption media into the sand area, the riser having a riserheight less than a baffle height, the influent directed into each of theone or more open channels passing through the sorption media toward theriser, effluent passing over the riser; and a perforated outlet pipe onan opposite side of the riser, the effluent passing through the outletpipe for disposal.

Further advantages of this invention will be apparent from the followingdetailed description of preferred embodiments which are illustratedschematically in the following section.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a schematic block diagram of a system used for the column testduring the batch study.

FIG. 2 a is a graph showing the gradation curve for Astatula sand.

FIG. 2 b is a graph showing the gradation curve for a first mixture usedfor material characterization.

FIG. 2 c is a graph showing the gradation curve for a second mixtureused for material characterization.

FIG. 3 is a schematic block diagram of an experimental design of amicrocosm study.

FIG. 4 a shows the sorption results for phosphorus in a linear form of aFreundlich isotherm model.

FIG. 4 b shows the sorption results for phosphorus in a linear form of aLangmuir isotherm model.

FIG. 5 shows an example of a passive underground drainfield according tothe present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Before explaining the disclosed embodiments of the present invention indetail it is to be understood that the invention in the context of autility patent is not limited in its application to the details of theparticular arrangements shown in this document since the invention iscapable of other embodiments. Also, the terminology used herein is forthe purpose of description and not of limitation. This invention isrelated to co-pending U.S. patent application Ser. No. 12/200,140 filedon Aug. 28, 2008 which is incorporated by reference.

The following descriptions focus on how these developed recipes usinggreen sorption media can help improve the performance of nutrientremoval in septic tank system as examples at University of CentralFlorida (UCF), in Orlando Fla.

Initially, the possible sorption media were screened through thefollowing five criteria: 1) the relevance of denitrification process, 2)the removal efficiency as evidenced in the literature with regard toadsorption, 3) the cost level, 4) the availability, 5) low maintenanceand 6) additional environmental benefits. Four sorption media wereselected for final consideration according to a multi-criteria decisionmaking (MCDM) process. The four sorption media include sawdust/woodchip, paper/newspaper, tire crumb and astatula sand (citrus grove sand).The two media mixes selected for use in the column tests are denoted asrecipe 1 which consists of approximately 68% fine sand, approximately25% tire crumb, and approximately 7% sawdust, and recipe 2 which iscomposed of approximately 69% fine sand, approximately 25% tire crumb,and approximately 6% paper/newspaper by volume. The reason for usingpaper in recipe 2 to replace sawdust in recipe 1 is that the electrondonor to triggering the denitrification process has to be present in themedia. At the end of the column tests, recipe 1 was further used forisotherm study and also as a media blend for microcosm system study.

The ASTM D-421-85 Standard Practice for Dry Preparation of Soil Samplesfor Particle-Size Analysis and Determination of Soil Constants was used.The Multi-point BET specific surface area by nitrogen adsorption methodwith respect to each type of recipe independently were performed byQuantachrome Instruments, which generated the surface area for these twomixed recipes as an average in the end. ASTM C29/C29M-07—was applied formeasuring the bulk density (“unit weight”) and voids in soil and mixedmedia. ASTM D-854-92 Standard Test Method for Specific Gravity of Soilswas applied for the determination of the specific gravity of soils andmedia that pass the 4.75-mm (No. 4) sieve.

A laboratory column test method is a physical model, which attempts tosimulate, on a small scale, a portion of the real world subsurfaceenvironment under a controlled set of experimental conditions. Labcolumn tests were conducted using three (2) plexi-glass columns 110 and115 as shown in FIG. 1. The columns 110 and 115 were approximately 0.29m inner diameter and approximately 1.5 m height and with recipe-1 andrecipe-2, respectively. The columns were packed in approximately 5 cmlifts by adding a pre-weighed dry sample. The final column porosity forboth the columns was approximately 40%. For sampling ports, the columnswere drilled with holes at approximately 1.37 m (4.5 ft) from the top ofthe media as shown in FIG. 1. Ball valves were used at the samplingports 120 and 125 and the ball valves were water sealed.

The composition of the columns in terms of weight and volume weredetermined as shown in Table 1. The feed solution, raw wastewater from afunctioning septic tank in Orlando, Fla., was stored for use in thecolumn study. Raw wastewater was pumped from the influent reservoir 130to the top of the columns as a continuous system. Each column wascovered with a lid at the top 112 and bottom 117 and the discharge ports140 were air tight to prevent direct contact of air thereby keeping thecolumns anoxic in condition. The flow of influent into the two columnswas controlled through a control panel 150 and the effluent dischargedfrom the bottom of each column drained into an effluent reservoir 160.The method of sampling included directly collecting effluent samplesfrom the bottom 117 of the columns 110 and 115 at the sampling port 120and 125, respectively. In this experiment, the sampling ports 120 and125 were air tight ball valves. The ball valves were opened and effluentsamples were extracted. The influent and effluent samples were collectedin sterilized plastic influent and effluent reservoir bottles 130 and160 and were transported for water quality analysis to ERD lab. Table 1shows the composition of columns in terms of weight and volume.

TABLE 1 Column STS Column STP wt % vol % wt % vol % Tire Crumb 10.9 25.010.7 25.0 Paper — — 4.0 6.2 Sawdust 4.0 7.1 — — Astatula Sand 85.1 67.985.3 68.8In table 1, STS is the acronym of Sand, Tire Crum and Sawdust (Recipe 1)and STP is the acronym of Sand, Tire Crum and Paper (Recipe 2).

Table 2 shows the results from the Column Study for Column STS andColumn STP with Recipe 1 and Recipe 2 respectively. During theexperimental period the columns did not show any signs of saturationwith nutrients although the columns were loaded with high concentrationsof nutrients with average total phosphorus concentration of 188 mg/Lwhich is approximately thirteen fold than the average concentration of14 mg/L for total phosphorus (USEPA, 2002) and average total nitrogenconcentration of 415 mg/L which is approximately eight fold than theaverage concentration of 50 mg/L for total nitrogen (USEPA, 2002).

TABLE 2 Avg Conc 19-Oct 26-Oct 10-Nov 17-Nov 30-Nov 2-Feb 26-Feb 7-Mar[mg/L] Nitrates Influent 0.27 0.31 3.02 3.49 3.10 0.16 0.21 1.95 1.56Recipe 1 0.04 0.06 0.08 0.02 0.15 0.01 0.01 0.02 0.05 Recipe 2 0.03 0.060.11 0.08 0.86 0.08 0.01 0.03 0.16 Average Percentage Removal (%);Recipe 1 = 97.0 & Recipe 2 = 90.1 Ammonia Influent 4.9 27.8 1.5 119 11210.7 72.9 — 49.7 Recipe 1 0.3 3.7 0.7 4.1 4.4 6.7 10.8 — 4.4 Recipe 20.1 0.2 0.0 0.1 0.8 0.9 11.0 — 1.9 Average Percentage Removal (%);Recipe 1 = 91.2 & Recipe 2 = 96.2 Total Nitrogen Influent 96.4 35.6 1135488 689 678 126 67.5 414 Recipe 1 6.2 6.4 5.3 4.2 5.2 6.9 12.1 10.3 7.1Recipe 2 5.1 7.0 6.5 5.7 5.4 1.1 15.9 0.9 6.0 Average Percentage Removal(%); Recipe 1 = 98.3 & Recipe 2 = 98.6 Ortho Phosphorus Influent 0.860.91 0.81 0.63 0.73 0.23 0.71 1.26 0.77 Recipe 1 0.01 0.00 0.02 0.040.00 0.00 0.00 0.00 0.01 Recipe 2 0.02 0.01 0.02 0.02 0.01 0.01 0.050.00 0.02 Average Percentage Removal (%); Recipe 1 = 98.8 & Recipe 2 =97.8 Total Phosphorus Influent 6.8 4.2 705 195 550 36.1 3.2 2.1 188Recipe 1 0.15 0.06 0.23 0.09 0.18 0.09 0.08 0.14 0.13 Recipe 2 0.21 0.080.19 0.15 0.21 0.19 0.07 0.07 0.15 Average Percentage Removal (%);Recipe 1 = 99.9 & Recipe 2 = 99.9 BOD Influent — — 2180 1475 7200 606173 198 1972 Recipe 1 — — 240 45.0 405 85.0 36.9 52.0 144 Recipe 2 — —751 750 833 342 2.00 48.0 454 Average Percentage Removal (%); Recipe 1 =92.7 & Recipe 2 = 76.7

In the previous study by Davis, Hunho Kim, Eric A. Seagren, Engineeredbioretention for removal of nitrate from stormwater runoff. WaterEnviron Res 75 no. 4 (2003), paper and sawdust showed some excellentresults in terms of nitrate removal and were accepted as one of the bestelectron donors. In this research, sawdust and paper (newspaper) showedsimilar results and were just not limited to nitrates but also to totalnitrogen, total phosphorus, ammonia, ortho-phosphorus and BOD. At theend of the experimental period, the newspaper print in the columns wasstill visible and most of the newspaper in the media mix remainedsimilar in appearance to the original material.

These observations are consistent with other studies that indicate thatnewspaper is somewhat resistant to bacterial degradation under anoxicconditions (Cummings and Stewart, 1994; Volokita et al, 1996; Davis etal, 2003). This resistance seems to be the chemical composition ofnewspaper, in particular the relatively high lignin content. Tire crumbthat was used for this research had a carbon content of 85% and did nothave any metal content. Though tire crumb was never used as anindividual media for the septic tank drainfield, the results indicatethat it has a strong potential for creating an environmentally safe andvalue-added option for scrap tire reuse.

Overall, the green sorption media showed significant potential forpollutant removal in a septic tank drainfield. Throughout theexperimental period, both columns showed approximately equal andconsistent removal of more than 90% for all the water quality parameters(i.e., ortho-phosphorus, total phosphorus, nitrates, total nitrogen,ammonia, BOD).

An Isotherm study as a batch process experiment was carried out usingrecipe 1 to study the sorption of ortho-phosphorus and nitrates. It ishelpful in determining the sorption capacity and also the estimated lifeof the media for the sorption of nutrients. For isotherm study ofnitrates, five flasks were prepared containing approximately 100 gm ofrecipe 1 and nitrate solution of approximately 50 mL of 9.6 mg/L, 8.4mg/L, 7.2 mg/L, 6.0 mg/L, 4.8 mg/L NO₃—N was added in each of the fivedifferent flasks. The media mix and the solution were mixed thoroughlyand kept for a residence time of twenty-four hours. After twenty-fourhours, a nitrate solution was extracted from the media and analyzed.

For the isotherm study of ortho-phosphates, one flask was preparedcontaining 200 gm of recipe 1 and a phosphate solution of 100 mL of 4.12mg/L PO₄—P. The media mix and the solution were mixed thoroughly andagain kept for a residence time of twenty-four hours. After twenty-fourhours, the phosphate solution was extracted from the media and analyzed.Using the same media mix in the flask 100 ml of fresh 4.12 mg/L PO₄—Pwas added to the flask and mixed thoroughly and resided for twenty-fourhours. The previous step was repeated for six days using the same mediamix and the extracted solutions from the media were analyzed.

The results for the nitrate and ortho-phosphate isotherm results arepresented in Table 3a and Table 3b, respectively. It can be seen fromTable 3a that there is very little or no removal of nitrates. It wasconcluded that the nitrates was not sorbed by the sorption media andbiological activity could not initiate as the batch studies wereperformed in twenty-four hours. However, substantial removal ofphosphorus was observed from the batch tests. The sorption results forphosphorus were plotted for the linearized form of Langmuir andFreundlich Isotherm Model as shown in FIGS. 4 a and 4 b respectively.The linearized form of Langmuir and Freundlich isotherm models are aspresented below:

TABLE 3a Mass Loading Mass Removed Sample [mg] [mg] 1 0.48 0.11 2 0.420.00 3 0.36 0.08 4 0.30 0.01 5 0.24 0.00

TABLE 3b Mass Loading Mass Removed Sample [mg] [mg] 1 0.41 0.35 2 0.410.27 3 0.41 0.23 4 0.41 0.21 5 0.41 0.17 6 0.41 0.12

Langmuir isotherm equation: (1/Q _(e))=(1/(Q _(max) b))×(1/C _(e))+(1/Q_(max))  (Eq. 1)

where: Q_(e)=Sorbed concentration [mass adsorbate/mass adsorbent];Q_(max)=Maximum capacity of adsorbent for adsorbate [mass adsorbate/massadsorbent]; b=Measure of affinity of adsorbate for adsorbent;C_(e)=Aqueous concentration of adsorbate [mass/volume].

Freundlich isotherm equation: log q _(e)=log K+(1/n)log C _(e)  (Eq. 2)

where: q_(e)=Sorbed concentration [mass adsorbate/mass adsorbent];K=Capacity adsorbent [mass adsorbate/mass adsorbent]; C_(e)=Aqueousconcentration of adsorbate [mass/volume]; n=Measure of how affinity forthe adsorbate changes with changes in adsorption density.

Assume that monolayer coverage of phosphorus adsorbed to the mediasurface. From the graphical plots as shown in FIGS. 4 a and 4 b, theadsorption capacity for phosphorus from the Langmuir and Freundlichisotherm models were calculated to be 34.4 mg g⁻¹ and 0 mg g⁻¹respectively. It is concluded that the Langmuir Equation fits better forthe sorption of phosphorus.

A Microcosm model is a small, representative system having analogies toa larger system in constitution, configuration and development. Amicrocosm model was built with a rectangular plastic container havingdimensions of Length=56 cm; Width=34.5 cm; Depth=15 cm. The model mainlyconsists of two zones, a treatment zone having a length of 46 cm and acollection zone of 10 cm. FIG. 3 shows the schematic diagram of theMicrocosm model system 200.

The bottom 5 cm of the treatment zone 210 consists of recipe 1 and theremainder of the model was packed with astatula sand. Syntheticwastewater flows into the model through the perforated tubing 220 which,in this experiment, had an inner diameter of 0.3 cm that acts as headerpipes and has a downward slope of approximately 1%. These perforatedtubes 220 are engineered with holes and slots, allowing the tubes 220 tocollect and disperse the wastewater from the influent reservoir 230 asit passes over the corrugations in the tubes 220. As the wastewater isdistributed throughout the tubes 220, it trickles down into the mediaallowing partial biological breakdown before reaching the media.

The wastewater was retained in the media for a hydraulic retention timeof seventy-two hours to provide the desired denitrification. Thewastewater was retained in the treatment zone with the help ofpre-fabricated riser 240 at approximately 46 cm length and approximately6.5 cm in height as shown in FIG. 2. The model is operationallycontrolled with control panel 250 to run as a continuous system andeffluent is collected from the collection zone 270 and/or sampled fromthe sampling port 280 connected with the effluent reservoir 260.Additionally, the locations of sampling ports 280 in the differentcompartments of the model are also shown in FIG. 2.

The permeability of the astatula sand was measured to be 55.0 cm/hr(21.6 in/hr). The permeability of recipe 1 and recipe 2 were measured tobe 54.4 cm/hr (21.4 in/hr) and 59.4 cm/hr (23.4 in/hr), respectively. Todetermine the particle-size distribution a sieve analysis was performed.Table 4 lists the summary of material characterization of the astatulasand and the two recipes used for the column tests. Surface area ofastatula sand, recipe 1 and recipe 2 were approximately 0.32 m² g⁻¹,0.08 m² g⁻¹ and 0.18 m² g⁻¹ respectively. Surface areas were determinedby a nitrogen sorption BET test (Quantachrome Instruments, BoyntonBeach, Fla.). FIGS. 3 a, 3 b, and 3 c show the gradation curve ofAstatula sand and two mixes used in our recipes comparatively.

TABLE 4 Astatula Sand Recipe 1 Recipe 2 Density (g cc⁻¹) 1.53 1.24 1.28Void Ratio (unit less) 0.73 0.69 0.62 Porosity (unit less) 0.42 0.410.38 Specific Gravity (Gs) 2.65 2.32 2.15 Surface Area (m2 g⁻¹) 0.320.08 0.18 Permeability (cm hr⁻¹) 55.0 54.4 59.4

The results from the Microcosm model are shown in Table 5. The samplesshowed approximately 80% removal efficiency for nitrates andortho-phosphorus. Additionally, the results also include theconcentration and removal efficiency from sampling ports located in thedifferent compartment of the model. It appears that most of thedenitrification reactions occur in the last compartment before the riserin the microcosm in which a well fostered anoxic environment can bemaintained throughout the operation. This observation is consistent withthe system design philosophy.

TABLE 5 Nitrates Ortho-Phosphorus Concentration % Cum % Concentration %Cum % [mg/L] Removal Removal [mg/L] Removal Removal Influent 2.38 1.28Sampling Port 1 2.33 1.87 1.87 1.15 10.17 10.17 Sampling Port 2 2.262.91 4.79 1.02 10.67 20.84 Sampling Port 3 1.72 22.68 27.47 0.76 20.3341.17 Sampling Port 4 0.49 52.03 79.50 0.23 40.91 82.08 Effluent 0.470.62 80.12 0.20 2.16 84.24

To determine the life of the green sorption media, which is applied as a5 cm (2 inch) layer in the microcosm model, only two factors need to beknown. These factors are the mass of the pollution control media and thephosphate mass loading rate per year. Knowing that the density of thegreen sorption media is 1.37 g cc⁻¹ (85.5 lbs ft⁻³), the mass of mediais 11,719 grams. Also knowing that the average concentration ofphosphorus coming into the drainfield is around 14 mg L⁻¹ (see Colman,J. A., 2005, Response curves for phosphorus plume lengths fromreactive-solute-transport simulations of onland disposal of wastewaterin noncarbonated sand and gravel aquifers: U.S. Geological SurveyScientific Investigations Report 2004-5299, 28p) and daily flow ofwastewater to the model was 1.25 L, the mass loading of phosphate yearis determined to be about 6,388 mg yr⁻¹. Additionally, the adsorptioncapacity from the batch isotherm tests for phosphorus was estimated tobe approximately 34.4 mg g⁻¹. The life of the green sorption media iscalculated to be approximately 63 years.

The information generated in the present study is valuable forunderstanding the postulated development of green sorption media appliedto solve the nutrient removal in an septic tank underground drainfield.Under the hydraulic retention time (HRT) of 24 hours, samples showedtreatment efficiencies of greater than 90% for both columns for allpollutants of concerns (FIG. 1). The batch adsorption isotherm data wasfitted in the Langmuir isotherm and Freundlich isotherm models, andadsorption capacity for phosphorus was found to be 34.4 mg g⁻¹ based onLangmuir isotherm (FIGS. 2 a, 2 b and 2 c). A microcosm (FIG. 3) of theseptic tank underground drainfield was built with one of the recipesapplied in the column test as a continuous system dosed with syntheticwastewater.

Under the HRT of 72 hours, samples from the microcosm physical modelshowed more than 80% of removal efficiency for nitrates and phosphorus(FIGS. 4 a and 4 b). Additionally, with the aid of the isotherm tests,the life expectancy of the proposed sorption media in the microcosmphysical model was estimated to be approximately 63 years for phosphorussorption. The significant removal efficiencies of the targetedcontaminants suggest that the use of the green sorption media is asuitable and powerful material for an in-situ remediation of nitrate andortho-phosphate contaminated in groundwater. Overall, this research andexperiments demonstrates the effectiveness of sawdust and paper aselectron donors in a drainfield whereas tire crumb may have betteradsorption capacity for nutrient removal.

An embodiment of the present invention provides a wastewater filtrationsystem for a passive drainfield. The system includes a green sorptionmaterial mixture consisting of one or more recycled materials mixed withone or more of a naturally occurring materials, a wetland cell filledwith the green sorption material mixture to provide an anoxicenvironment, the wetland cell including baffled compartments and a riserto host the anoxic environment, an influent distribution system todistribute the influent over the wetland cell, and a piping systemarranged for dosing the wetland cell to sustain the functionality of thegreen sorption material mixture in the passive drainfield to remove anutrient content in wastewater. Proper design of hydraulic residence orretention time with appropriate baffled compartments and riser must bewell configured to host an anoxic environment. Such passive undergrounddrainfield system can then possess the capability to effectively removethe nutrient content in septic tank effluents and other waste streams incontaminated wastewater/groundwater systems

The group of recycled materials includes tire crumb, sawdust, orangepeel, coconut husks, leaf compost, oyster shell, and soy bean hulls,tree bark, wood chips, paper, alfalfa, mulch, cotton and wheat straw andthe group of naturally occurring materials includes peat, sands,zeolites and clay. In an embodiment, the green sorption material mixtureincludes approximately 68% fine sand, approximately 25% tire crumb, andapproximately 7% sawdust by volume. In another embodiment, the greensorption material mixture includes approximately 69% fine sand,approximately 25% tire crumb, and approximately 6% paper/newspaper byvolume. In an embodiment, one of the one or more recycled materials isselected from a subgroup including sawdust and paper as electron donorsin a drainfield and the recycled material is tire crumb for nutrientremoval based on an adsorption capacity of the tire crumb.

The filtration system can be an on-site wastewater treatment system, apassive underground drainfield to remove a nutrient content in septictank effluents and other waste streams in contaminatedwastewater/groundwater systems, a passive underground drainfield toremove a nutrient content in contaminated wastewater/groundwater system,a septic tank system, and/or an in-situ remediation of nitrate andortho-phosphate contaminated in groundwater.

FIG. 5 shows the design drawing of this passive underground drainfield.Household sewerage can be directed into the underground drainfield withsorption media being placed in an open channel within the boxpartitioned by a few baffles. The total number of battles requireddepends on how long the retention time is needed. Spraying the seweragein the front section of the manifold (inflow pipe) happens periodically.Perforated pipes at the front section can promote the aeration tomaintain the aerobic condition at the first part of channel. Then thebaffles can guide the flow through the open channel smoothly. While thefirst part of the channel consumes a lot of air for nitrification, thedissolved oxygen would gradually change to zero making the subsequentprocess anoxic and aerobic before the riser where denitifcation mayoccur constantly. All sections before the riser in the open channel mustbe filled with sorption media to promote the targeted reactions. Afterhaving 3-5 days retention time, flow will eventually pass through aperforated outlet pipe that completely partitions the reaction box andthe disposal box. Infiltrate will seep down into the vadose zonegradually in the end. This type of design can fit into both undergrounddrainfield with soil substitution and elevated mound system associatedwith a variety of treatment processes. A pilot plant has beenconstructed at the University of Central Florida, Orlando, Fla.

The passive underground drainfield 500 shown in FIG. 5 includes anunderground drainfield filled with a green sorption media 510 andportioned by one or more baffles 520 located on the sorption media 510to create one or more open channels, the baffles 520 guiding a flow ofinfluent following the flow path shown through the open channel into thesorption media. The system includes a distribution system for directingan influent into the underground drainfield, the distribution systemincluding perforated inlet pipes 530 in each of the one or more openchannels to promote aeration to maintain an aerobic condition in eachchannel and an air inlet port 540 in each of the one or more channelsfor drawing air for nitrification for an anoxic and aerobic environmentwhere denitifcation occurs. A riser 550 located at one end of theunderground drainfield in the sorption media 510 and extending adistance above the sorption media into the sand area, the riser 550having a riser height less than a baffle height, the influent directedinto each of the one or more open channels passing through the sorptionmedia toward the riser 550, effluent passing over the riser 550; and aperforated outlet pipe 560 on an opposite side of the riser 550, theeffluent passing through the outlet pipe 560 for disposal.

Another embodiment provides a method for on-site wastewater treatment byproviding a horizontal underground cell including baffled compartmentsand a riser to host an alternating cycle of aerobic and anoxicenvironments, mixing one or more recycled material selected from a groupconsisting essentially of tires, sawdust and food waste and one or morenaturally occurring materials as a green sorption material mixture,filling the horizontal underground cell with a green sorption materialmixture to provide an anoxic environment and providing a piping systemfor dosing the horizontal underground cell with an influent to sustainthe functionality of the green sorption material mixture in the passivedrainfield to remove a nutrient content in wastewater. The method can beused in conjunction with underground septic tank systems as analternating cycle of aerobic and anoxic environments to remove nutrientcontent from the influent.

In summary, pollutants of concern include nitrates, ammonia, totalnitrogen, ortho-phosphorus, total phosphorus and BOD. Sorption media ofinterest include but are not limited to tire crumb, tree bark, woodchips, sawdust, paper (newspaper), alfalfa, mulch, cotton, wheat strawand sulfur/limestone. Two recipes with mixed sorption media wereselected in the end of the initial literature for columns study. At theend of the column study, the recipe including sand, tire crumb andsawdust was further used to estimate the sorption life of the media mixand also as a media mix for the design of microcosm physical model. Thedrainfield shoWn in FIG. 5 is for illustration purposes only, thoseskilled in the art will understand that alternative configurations areavailable within the scope of the present invention.

While the invention has been described, disclosed, illustrated and shownin various terms of certain embodiments or modifications which it haspresumed in practice, the scope of the invention is not intended to be,nor should it be deemed to be, limited thereby and such othermodifications or embodiments as may be suggested by the teachings hereinare particularly reserved especially as they fall within the breadth andscope of the claims here appended.

1-15. (canceled)
 16. A green sorption media consisting of: one or morerecycled materials selected from a group consisting of selected from agroup consisting of tire crumb, sawdust, orange peel, coconut husks,leaf compost, crushed oyster shell, soy bean hulls, tree bark, woodchips, paper, alfalfa, mulch, cotton and wheat straw; one or more of anaturally occurring materials selected from a group consisting of peat,sand, zeolites, limestone, sulfur and clay mixed with the one or morerecycled materials.
 17. The green sorption material of claim 16, whereinone of the one or more recycled materials is selected from a subgroupincluding sawdust and paper as an electron donor.
 18. The green sorptionmedia of claim 17 wherein the one of the one or more recycled materialsfurther includes tire crumb for nutrient removal.
 19. The green sorptionmaterial of claim 18 wherein the tire crumb for nutrient removal doesnot have a metal content.
 20. The green sorption media of claim 18wherein the one or more naturally occurring materials is sand.
 21. Thegreen sorption material of claim 20, wherein the green sorption materialmixture consists of: sand, tire crumb and sawdust.
 22. The greensorption material of claim 21, wherein the green sorption materialmixture consists of: approximately 68% sand, approximately 25% tirecrumb and approximately 7% sawdust by volume.
 23. The green sorptionmedia of claim 20 wherein the one or more recycled materials consists ofpaper as an electron donor to trigger a denitrification process, thepaper mixed with tire crumb.
 24. The green sorption material of claim 23consisting of: sand, tire crumb and paper.
 25. The green sorptionmaterial of claim 24 consisting of: approximately 69% sand,approximately 25% tire crumb, and approximately 6% paper by volume.